Alternative structures of RNA control gene expression and offer therapeutic strategies

RNA viruses are diverse and abundant pathogens responsible for numerous human ailments, from common colds to AIDS, SARS, Ebola, and other dangerous diseases. RNA viruses possess relatively compact genomes and have therefore evolved multiple mechanisms to maximize their coding capacities, often using overlapping reading frames. In this way, one RNA sequence can encode multiple proteins via mechanisms including alternative splicing and ribosomal frameshifting. Many such processes in gene expression involve the RNA folding into three-dimensional structures that can recruit ribosomes without initiation factors, hijack host proteins, cause ribosomes to frameshift, and expose or occlude regulatory protein binding motifs to ultimately control each key process in the viral life cycle. I will discuss the RNA structure of HIV-1 and SARS-CoV-2 and the importance of alternative conformations assumed by the same RNA sequence in controlling gene expression of viruses and bacteria.Copyright © 2023 The American Society for Biochemistry and Molecular Biology, Inc.

VHH DIMER P559-R45L NEUTRALIZES SARS-CoV-2 BY STABILIZING SPIKE IN UP CONFORMATION

Background: SARS-CoV-2 Omicron subvariants are highly resistant to vaccineinduced immunity and therapeutic monoclonal antibodies. We previously reported anti-SARS-CoV-2 spike alpaca nanobodies (VHHs) P86 and P17 that potently neutralize the wild type and VOCs from Alpha to Omicron BA.1 and BA.2, but not Omicron subvariants after that such as BA.4/5. Thus, we tried to establish a new VHH that can neutralize all the variants including BA.4/5. Method(s): We developed VHH trimers and heterodimers based on the structural and computational analysis of Delta spike-immunized alpaca VHH library. We tested representative VHHs against SARS-CoV-2 spike by pseudovirus assays and generated VHH heterodimers. We further obtained Cryo-EM structure of Spike trimer and VHH monomer or heterodimer. Result(s): First, we generated series of P86 mutants to counteract L452R mutation in Delta or Omicron BA.5 subvariants and found that P86 R45L was most potent against D614G with an IC50 of 0.03 mug/mL. From the Delta spike-immunized VHH library, we also identified that homo-trimer of a new clone P559 neutralized SARS-CoV-2 Delta and Omicron BA.5 variants with an IC50 of 0.077 and 0.54 mug/mL, respectively. We finally generated P559-R45L heterodimer that neutralized all the variants so far including Omicron BA.5 with an IC50 of 0.39 mug/mL. Cryo-EM structure revealed that three molecules of P559- R45L heterodimer bridged two RBD molecules in the spike trimer and stabilized spike timers with RBD in the up conformation. Conclusion(s): We developed VHH P559-R45L heterodimer that potently neutralized all the variants including Omicron subvariants through unique structural interaction.

Study on Molecular Docking of 'Nucleocapsid (N) Protein of Sars-Cov-2' and 'Mcf-7'

The process of eliminating viral infection and massive control from spreading furthermore by any variants may lead to a pandemic in the near future. On the other aspect, the impact of eradicating by the initial stage to prevent, treat carcinoma to decline the affected and death rate to maximum amount by Molecular Docking. The quickest and easiest method to search out the potential drugs is by analyzing the ligand-protein interactions compared to the traditional ways. Drugs of antivirals and anti-cancer drugs are given for treating viral infections and cancers. Massive kinds of viruses affect humans with several diseases, from self-curable diseases to acute mortal diseases. In cancer, the diseases are known by the cells within humans;multiplication occurs and forming the tumors of malignant cells with the flexibility to be a pathological process. Herbal medicines are known to play enormous role by giving initial priority. Various plant species are being employed to cure or prevent viral infections and cancers. Molecular docking provides a fast understanding of the ligand's exploration of conformations, poses among drug targets' binding sites, and predicts the binding affinity of protein-ligand. Its main approach is to spot top-ranked conformations on compounds and means of docking to the active site of target of interest. Intake of naturally suggested fruits and vegetables leads to the goal of decreasing the death rate, and the count of females who are liable to breast cancers.Copyright All © 2023 are reserved by International Journal of Pharmaceutical Sciences and Research.

Molecular Docking and Dynamics of Phytochemicals From Chinese Herbs With SARS-CoV-2 RdRp

The novel Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is causing coronavirus disease 2019 (COVID-19) pandemic. Ancient Chinese herbal formulas are effective for diseases caused by viral infection, and their effects on COVID-19 are currently being examined. To directly evaluate the role of Chinese herbs in inhibiting replication of SARS-CoV-2, we investigated how the phytochemicals from Chinese herbs interact with the viral RNA-dependent RNA polymerase (RdRP). Total 1025 compounds were screened, and then 181compounds were selected for molecular docking analysis. Four phytochemicals licorice glycoside E, diisooctyl phthalate, (-)-medicocarpin, and glycyroside showed good binding affinity with RdRp. The best complex licorice glycoside E/RdRp forms 3 hydrogen bonds, 4 hydrophobic interactions, 1 pair of Pi-cation/stacking, and 4 salt bridges. Furthermore, docking complexes licorice glycoside E/RdRp and diisooctyl phthalate/RdRp were optimized by molecular dynamics simulation to obtain the stable conformation. These studies indicate that they are promising as antivirals against SARS-CoV-2.Copyright © The Author(s) 2022.

Studying the Predictive Effects of Bacterial Carotenoids in the Treatment of Endometriosis Using Virtual Screening Methods

Background: Endometriosis is a chronic inflammatory disease defined as the presence of endometrial tissue outside the uterus, which causes pelvic pain and infertility. Cytokines appear to play vital roles in the development and progression of endometriosis and associated infertility. Tumor necrosis factoralpha (TNF-alpha) is a multifunctional pro-inflammatory cytokine, responsible for autoimmune and inflammatory disorders. TNF- alpha plays an important role in endometrial physiology as well as during early implantation. In addition, this cytokine has a considerable pathophysiological function in diseases such as menorrhagia, endometriosis, or infertility due to its regulatory impact on proliferation, differentiation, and angiogenesis in the human endometrium. In women with endometriosis, TNF-alpha levels increases in peritoneal fluid and serum significantly. In the present study, we focused on finding novel small molecules that can directly block TNFalpha- hTNFR1 (human TNF receptor 1) interaction. Method(s): In this regard, TNF-alpha inhibiting capacity of natural carotenoids was investigated in terms of blocking TNF-alpha-hTNFR1 interaction with the help of a combination of in silico approaches, based on virtual screening, molecular docking, and molecular dynamics (MD) simulation. Result(s): A total of 125 carotenoids were selected out of 1204 natural molecules, based on their pharmacokinetics properties, and they all met Lipinski's rule of five. Among them, sorgomol, strigol, and orobanchol had the most favorable DELTAG with the best pharmacokinetics properties and were selected for MD simulation studies, which explored the complex stability and the impact of ligands on protein conformation. It was shown that sorgomol formed the most hydrogen bonds, resulting in the highest binding energy with the lowest RMSD and RMSF. Conclusion(s): Our results showed that sorgomol was the most appropriate candidate as a TNF-alpha inhibitor. In conclusion, the present study could serve to expand possibilities to develop new therapeutic small molecules against TNF-alpha which plays an important role in the inflammation of endometriosis.

Missense Variants of von Willebrand Factor in the Background of COVID-19 Associated Coagulopathy.

COVID-19 associated coagulopathy (CAC), characterized by endothelial dysfunction and hypercoagulability, evokes pulmonary immunothrombosis in advanced COVID-19 cases. Elevated von Willebrand factor (vWF) levels and reduced activities of the ADAMTS13 protease are common in CAC. Here, we aimed to determine whether common genetic variants of these proteins might be associated with COVID-19 severity and hemostatic parameters. A set of single nucleotide polymorphisms (SNPs) in the vWF (rs216311, rs216321, rs1063856, rs1800378, rs1800383) and ADAMTS13 genes (rs2301612, rs28729234, rs34024143) were genotyped in 72 COVID-19 patients. Cross-sectional cohort analysis revealed no association of any polymorphism with disease severity. On the other hand, analysis of variance (ANOVA) uncovered associations with the following clinical parameters: (1) the rs216311 T allele with enhanced INR (international normalized ratio); (2) the rs1800383 C allele with elevated fibrinogen levels; and (3) the rs1063856 C allele with increased red blood cell count, hemoglobin, and creatinine levels. No association could be observed between the phenotypic data and the polymorphisms in the ADAMTS13 gene. Importantly, in silico protein conformational analysis predicted that these missense variants would display global conformational alterations, which might affect the stability and plasma levels of vWF. Our results imply that missense vWF variants might modulate the thrombotic risk in COVID-19.

Molecular Docking and the Pharmacokinetic Properties of the Anti-Viral Compounds Towards SARS-CoV- An In-silico Approach

The main aim of this study is to determine the bioactive compounds which have drug-like properties and has the potential to combat the spike-glycoprotein of SARS-CoV-2. The 6LXT protein of covid-19 was chosen from the protein data bank as a target protein. The compounds which are potentially capable to bind with the target were picked from the PubChem database and docked using the tool Autodock 4.2. Molecular docking of the molecules was done with the best conformations of the ligands and grid size was selected according to the hit compounds' interaction with the target protein. The ligand binding sites with the target molecules were predicted using MetaPocket 2.0. The docking Score of 50 compounds wascarried out and also toxicity studies were carried out. The compounds selected were calculated to identify the best conformations having drug-likeness properties. The top 10 compounds were chosen for the structure-activity relationship based on their binding interactions with the protein and ligand. The ligands then underwent the pharmacokinetic analysis followed by Lipinski's and all the results were finalized and categorized. ManzamineA, Imatinib, and basotinib were elected as the peak compounds with the binding energy -9.01kcal/mol, -8.71kcal/mol, and -8.01kcal/mol.

Characterization of SARS-CoV-2 Isolate (MZ558159) for in Silico Drug Designing, Reported from India

Introduction: Inadequate information available about the genomics and proteomics characterization of SARS-CoV-2 isolates reported from India and other part of the globe. This characterization is important for the in silico drug designing as there are no approved medications available to treat SARS-CoV-2 infection. Aim(s): The aim of the present study is characterization of SARS-CoV-2 (MZ558159) isolate reported from India using homology modelling, validation and in silico drug designing methods. Material(s) and Method(s): Genome sequence of SARS-CoV-2 (MZ558159) was retrieved from NCBI, and four protein sequences selected for the homology modeling, validation and in silico drug designing e.g., QXN18496, QXN18498, QXN18504, and QXN18497. SWISS-MODEL and UCLA-DOE server used for homology modeling. Validation for structure model performed using PROCHECK and molecular docking using MCULE-1-Click server. Result(s): The surface glycoprotein (QXN18496) model corresponding to probability conformation with 93.6%, envelope protein (QXN18498) with 88.9%, nucleocapsid phosphoprotein (QXN18504) with 93.6%, and ORF3a protein (QXN18497) with 91.8% residues in core section of o-o plot that specifies accuracy of prediction model. The corresponding ProSA Z-score score -12.67, -0.01, -4.4, and -2.87 indicates the good quality of the models. Molecular dynamic simulation and docking studies revealed the inhibitor binds effectively at the SARS-CoV-2 (MZ558159) proteins. Predicted inhibitor 2-acetamido-2-deoxy-beta-D-glucopyranose exhibited effective binding affinity against surface glycoprotein (QXN18496). Conclusion(s):The results of study establish inhibitor 2-Acetamido-2-deoxy-beta-D-glucopyranose as valuable lead molecule with great potential for surface glycoprotein (QXN18496).

Wavelet-based Spectral Analysis For Protein Conformation Selection and Prediction Using AI in Drug Discovery Applications

Contemporary drug discovery relies heavily on massive high performance computing (HPC) resources from docking and molecular dynamics simulations of proteins interacting with drug candidate ligands, such as recently published form simulations on ORNL's SUMMIT in covid19 pharmaceutical research. This work presents a unique spectral analysis approach using wavelet transform (WT) to understand the correlation between the time evolution of protein conformations generated by molecular dynamics and specific protein conformations that are selected for binding by ligands. A DWT-based spectral analysis is performed on the unique protein descriptors previously identified to be important in protein: ligand binding. The new protein time-series information from the wavelet-based time-frequency domain analysis is used for a more refined protein conformation selection and improve the deep learning and machine learning (AI/ML) prediction framework to improve the prediction of binding vs. non-binding protein conformations for three target proteins ADORA2A, OPRD1 and OPRK1. In this work, wavelets are used for spectral analysis for their added benefit of simultaneous time-frequency resolution and denoising properties. © 2022 IEEE.

Study of Marine Natural Products as Anti-SARS-CoV-2 Agents Using Molecular Modeling

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has created a global pandemic. Viral entry into host cells is mediated by spike glycoprotein (SGP) interactions with angiotensin-converting enzyme 2 (ACE2) and heparan sulfate glycosaminoglycans on the cell surface. Carbohydrate small molecules were found to bind to the receptor binding domain (RBD) of SGP, which also interacts with ACE2, forming a ternary complex. Moreover, glycans isolated from sea cucumber and red alga species exhibited anti-SARS-CoV-2 activities, presumably by blocking viral entry mediated through SGP-heparan sulfate interactions. Here we report a collection of computational studies conducted as part of a collaborative effort to investigate the effects of marine natural products (NPs) on the wild-type and N501Y mutant SGP RBD. Starting from an X-ray crystal structure of the RBD-ACE2 complex, a model of SGP RBD was built. To investigate the static and dynamic behavior of RBD-NP interactions, blind and site-targeted molecular docking using diverse docking programs (Glide, AutoDock Vina or ClusPro) was carried out, followed by extensive molecular dynamics simulations with two force fields (CHARMM36 or Glycam06) and binding free energy calculations. Predicted conformations of the NPs varied considerably when modeled in water or in complex with RBD. Five NP binding sites on the RBD were studied. NP binding specificities towards SARS-CoV-2 variants were explained and important RBD residues were identified. Statistical analyses of the stability of various protein-NP complexes during molecular dynamics simulations helped to differentiate pseudo-vs. real-binding sites. Our results provide significant insights into the importance of extensive molecular dynamics calculations in order to move beyond the limitations of molecular docking.

Lapachol and (alpha/beta)-lapachone as inhibitors of SARS-CoV-2 Main Protease (Mpro) and hACE-2: ADME properties, docking and dynamic simulation approaches

Background: Tabebuia impetiginosa is an important medicinal plant rich in lapachol, alpha-lapachone, and beta-lapachone known to possess several biological activities. Objective(s): In this study, we investigated the drug potential of lapachol, alpha-lapachone, and beta-lapachone using molecular docking, molecular dynamic (MD), and drug-likeness properties. Material(s) and Method(s): The computational study was performed using SwissADME software for the determination of the pharmacokinetic properties of the tested compounds. AutoDock Vina and Genetic Optimization for Ligand Docking (GOLD) were used for the docking analysis, and MD simulations were run using Schrodinger's Desmond Simulation. Result(s): The three compounds lapachol, alpha-lapachone, and beta-lapachone binds to cysteine (Cys)-histidine (His) catalytic dyad (Cys145 and His41) along with the other residues with, respectively, the following docking score 48.69, 47.06, and 47.79. Against viral entry receptor, human angiotensin-converting enzyme 2 (hACE-2), alpha-lapachone exhibited the highest GOLD Fitness score complex (54.82) followed by lapachol (42.53) and beta-lapachone and hACE-2 (38.74) generating several active sites in the target proteins. A 100 ns MDs simulation study revealed the stable conformation of bioactive compounds within the cavity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) of hACE-2 protein and main protease (Mpro). From the dynamic study, it was observed that lapachol was tightly bound with catalytic dyad residue Cys145 of Mpro with more than 40% time of simulation, also post-simulation MM-GBSA binding free energy (DELTAG Bind) revealed the highest energy score (-51.18 +/- 5.14 kcal/mol) among the evaluated complex. Moreover, the absorption, distribution, metabolism, and excretion (ADME) properties demonstrated that the investigated compounds passed the pharmacokinetic and drug-likeness criteria without undesirable effects. Conclusion(s): The computational study highlighted that these compounds could be highly recommended and developed as part of an effective drug against the SARS-CoV-2 virus. Copyright © 2022 Pharmacognosy Magazine.

SARS-CoV-2 variants impact RBD conformational dynamics and ACE2 accessibility

The coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has killed over 5 million people and is causing a devastating social and economic impact all over the world. The rise of new variants represents a difficult challenge due to the loss of vaccine and natural immunity, and increased transmissibility. These variants contain mutations in the spike glycoprotein, which mediates fusion between the viral and host cell membranes, via its receptor binding domain (RBD) that binds to angiotensin-converting enzyme 2 (ACE2). To understand the effect of RBD mutations, a lot of attention has been given to the RBD-ACE2 interaction. However, this type of analysis is limited since it ignores the conformational dynamics of the RBD itself. Observing that some variants mutations occur in residues that are not in direct contact with ACE2, we hypothesized that they could affect RBD conformational dynamics. To test this, we performed long atomistic molecular dynamics simulations to investigate the structural dynamics of wt RBD, and that of three variants (alpha, beta and delta). Our results show that in solution, wt RBD presents two distinct conformations: an 'open' conformation where it is free to bind ACE2;and a 'closed' conformation, where the RBM ridge blocks the binding surface. The alpha and beta variants significantly impact the open/closed equilibrium, shifting it towards the open conformation by roughly 20%. This shift likely increases ACE2 binding affinity. In the delta variant RBD simulations, the closed conformation was never observed. Instead, the system alternated between the before mentioned open conformation and an alternative 'reversed' one, with a significantly changed orientation of the RBMridge flanking the RBD. These results support the hypothesis that variants impact RBD conformational dynamics in a direction that simultaneously promotes efficient binding to ACE2 and antibody escape.

SARS-CoV-2 VARIANTS INCREASE KINETIC STABILITY of OPEN SPIKE CONFORMATIONS

Background: SARS-CoV-2 variants of concern harbor mutations in the Spike (S) glycoprotein that confer more efficient transmission and dampen the efficacy of COVID-19 vaccines and antibody therapies. S mediates virus entry and is the primary target for antibody responses, with structural studies of soluble S variants revealing an increased propensity towards conformations accessible to the human Angiotensin-Converting Enzyme 2 (hACE2) receptor. However, real-time observations of conformational dynamics that govern the structural equilibriums of the S variants have been lacking. Methods: Here, we report single-molecule Förster Resonance Energy Transfer (smFRET) studies of S variants of concern containing critical mutations, including D614G and E484K, in the context of virus particles. Results: Investigated variants were shown by smFRET to predominantly occupy more open hACE2-accessible conformations, agreeing with predictions from structures of soluble trimers. Additionally, S variants exhibited decelerated transitions from hACE2-accessible/bound states. Conclusion: Here, we provide the real-time dimension to distinct structures of Spikes in the context of virus particles and present the first experimental evidence of increased stability of Spike variants. Our finding of increased S kinetic stability in the open conformation provides a new perspective on SARS-CoV-2 adaptation to the human population.

STRUCTURAL CHARACTERIZATION of DNA-ENCODED HIV VACCINES INDUCED NEUTRALIZING ANTIBODY

Background: Rapid and large-scale deployment of COVID-19 mRNA vaccines highlights the potential utility of developing nucleic acid vaccines (such as RNA and DNA vaccines) against infectious diseases, including HIV-1. However, as compared to SARS-CoV-2, HIV-1 pose some unique challenges-induction of neutralizing antibodies (NAbs) against HIV-1 (frequently a correlate of protection) requires presentation of trimeric and highly conformational epitopes to the immune system, and whether nucleic acid vaccines can enable direct in vivo production of antigens that retain critical antigenic profile has not yet been elucidated. Additionally, it was previously reported that Tier 2 NAbs cannot be induced in mice due to a lack of antibody repertoire, and vaccine studies were suggested to be performed in larger mammals such as rabbits/NHPs, inadvertently slowing down and increasing the costs of preclinical HIV-1 vaccine studies. Methods: In our study, we used the Antigen Conformation Tracing In Vivo by ELISA (ACTIVE) assay developed in house to characterize antigenic profiles of vaccines produced in vivo (from transfected muscle tissues). We analyzed induced cellular responses, using stimulation with overlapping peptides followed by intracellular cytokine staining and IFN-g ELIspot assays. We analyzed induced humoral responses by using both binding ELISA assays and TZM-BL based neutralizing assays, and attempted to map induced NAb epitopes by engineering selectively mutated pseudovirus. We performed antigen-specific B-cell sorting, and used the 10x genomics pipeline to characterize antibody sequences of proliferating B-cell clones. Results: We confirmed that in vivo produced vaccines retained key trimeric conformational epitopes and glycan profiles. Compared to protein vaccination, DNA vaccination uniquely and strongly induced both TFH, CD4+, CD8+ T-cell responses, and Tier 2 NAbs mapped to a previously unreported Env C3/V5 epitope. 5 unique NAbs were isolated, and confirmed to bind to the epitope using a Cryo-EM structure of NAb-MD39 complex at 3.8Å resolution. Conclusion: Our study confirmed that with appropriate vaccine delivery technology, murine models can be appropriately used for HIV-1 vaccine studies aimed at generating NAb responses. In addition, beyond potential functional immunity gains, DNA vaccines permit in vivo folding of structured antigens and provide significant cost and speed advantages for enabling rapid evaluation of new HIV vaccines.

DESIGN of NOVEL and HIGHLY SELECTIVE SARS-CoV-2 MAIN PROTEASE INHIBITORS

Background: SARS-CoV-2 has caused a global pandemic, yet despite vaccine availability, it continues to inflict morbidity and mortality worldwide. The viral main protease (Mpro) is highly conserved across multiple coronaviruses and has a unique viral substrate specificity. Thus, highly selective Mpro inhibitors are expected to be safe, effective, and elude drug resistance for future coronaviruses. Methods: We used a conformationally restricted peptidomimetic to mimic the bioactive conformation of the Mpro-substrate complex to identify potent, selective Mpro inhibitors. We evaluated protease inhibition in biochemical assays, and cellular efficacy in Vero-E6 cells challenged with live virus representing parental (USA-WA1/2020), beta (B.1.351), and delta (B.1.617.2) variants by monitoring infection at day 2 post-infection measuring nucleocapsid-positive cells by high content imaging, and cytopathic effect (CPE) at day 4 post-infection using resazurin viability dye. Results were compared to reference compounds. Group differences were analyzed by two-sided, paired t-test. Results: AP-8-013 required a 2-hour incubation to achieve maximal dose-dependent Mpro inhibition with an IC50 = 230 ± 18 nM, reflecting its highly constrained conformation, compared to the more flexible Cpd 22 (AP-8-001;IC50 = 11 ± 0.7 nM) or GC-376 (IC50 = 18 ± 1.5 μM). Importantly, AP-8-013 showed exquisite selectivity for Mpro with no inhibition at key mammalian cysteine proteases, cathepsin B and L, or the serine protease thrombin, while Cpd 22 (Cat B IC50 = 24 ± 7.5 nM, Cat L IC50 = 1.8 ± 0.3 nM) or GC-376 (Cat B IC50 = 37 ± 1.5 nM, Cat L IC50 = < 1 nM) showed poor selectivity towards mammalian cysteine proteases. AP-8-013 was active in CPE cell-based assays with comparable potency to reference compounds, with EC50 = 4.7 μM compared to Cmp 22 (EC50 = 1.4 μM) or GC-376 (EC50 = 1.1 μM). Using intact SARS-CoV-2 infection-based assays, AP-8-013 significantly inhibited parental virus as well as beta and delta VOC (EC50s = 2.7, 2.5, and 6.0 μM, respectively). Finally, a 3:1 molar mixture of AP-8-013 and remdesivir significantly enhanced antiviral activity in CPE assays (EC50 = 1.3 μM;p < 0.05) when compared against either compound alone (EC50s = 4.7 and 3.3 μM, respectively). Conclusion: We have identified a novel drug-like Mpro inhibitor lead series which is highly selective over cysteine and serine proteases that can inhibit multiple SARS-CoV-2 VOC and increase the antiviral activity of remdesivir.

MANNOSE-BINDING LECTIN (MBL) INHIBITS SARS-CoV-2 INFECTION and REPLICATION in VITRO

Background: Humoral innate immunity consists of a limited, but diverse, set of humoral fluid phase pattern recognition molecules (PRMs) that represent a first line of resistance against microbial invaders by promoting pathogen disposal by phagocytosis, complement activation and inflammation. These factors encompass complement, ficolin, collectin and pentraxin family of proteins. Methods: We have analyzed the activity of PRMs for their potential capacity of inhibiting SARS-CoV-2 entry and replication into epithelial cells by a microneutralization assay based on a lentiviral particles pseudotyped with the SARS-CoV-2 spike protein in HEK293T cells overexpressing the angiotensin converting enzyme 2 (ACE2). Either SARS-CoV-2 or target cells were incubated with Mannose Binding Lectin (MBL, concentration range: 1-50 μ g/ml) to further characterize its anti-viral activity for 1 h prior to infection in both human Calu-3 cells and air-liquid interface cultures of human bronchial epithelial cells (HBEC). Binding experiments were carried out with SARS-CoV-2 Spike protein and recombinant MBL to further investigate its antiviral action. Results: Among 12 PRMs tested, only MBL inhibited viral entry in the pseudotyped neutralization assay. Furthermore, MBL protein inhibited SARS-CoV-2 viral replication in Calu-3 and HBEC by ca. one log10 at the top concentration (10 μ g/ml and 50 μ g/ml, respectively). MBL antiviral activity was confirmed also against alpha, beta and gamma SARS-CoV-2 variants of concern. Binding experiments showed that MBL specifically interacts with the trimeric form of SARS-CoV-2 spike. Conclusion: MBL binds to the Spike protein in its active trimeric conformation leading to the inhibition of SARS-CoV-2 infection and replication in vitro. These results suggest that MBL possesses an antiviral activity against SARS-CoV-2 that could bear therapeutic potential.

Structure and function of SARS-CoV-2 spike protein and its receptor

Corona virus disease 2019 is an acute infectious disease caused by SARS-CoV-2 infection and has entered the state of global pandemic. Spike protein ( S protein) , a key protein that mediates SARS-CoV-2 to infect host cells, has the characteristics of specific receptor binding and membrane fusion, playing an important role in host tropism and virulence. The spontaneous closed and open conformation of S protein trimer is crucial for receptor binding and initiation of conformational changes in membrane fusion, and its unique furin recognition site may be a crucial factor leading to high infectivity. Therefore, to study the structure and function of SARS-CoV-2 S protein and its receptor has important implications for invasion mechanisms of SARS- CoV-2 and the development of relevant targeted drugs.

A Structural Comparison of SARS-CoV-2 Main Protease and Animal Coronaviral Main Protease Reveals Species-Specific Ligand Binding and Dimerization Mechanism.

Animal coronaviruses (CoVs) have been identified to be the origin of Severe Acute Respiratory Syndrome (SARS)-CoV, Middle East respiratory syndrome (MERS)-CoV, and probably SARS-CoV-2 that cause severe to fatal diseases in humans. Variations of zoonotic coronaviruses pose potential threats to global human beings. To overcome this problem, we focused on the main protease (Mpro), which is an evolutionary conserved viral protein among different coronaviruses. The broad-spectrum anti-coronaviral drug, GC376, was repurposed to target canine coronavirus (CCoV), which causes gastrointestinal infections in dogs. We found that GC376 can efficiently block the protease activity of CCoV Mpro and can thermodynamically stabilize its folding. The structure of CCoV Mpro in complex with GC376 was subsequently determined at 2.75 Å. GC376 reacts with the catalytic residue C144 of CCoV Mpro and forms an (R)- or (S)-configuration of hemithioacetal. A structural comparison of CCoV Mpro and other animal CoV Mpros with SARS-CoV-2 Mpro revealed three important structural determinants in a substrate-binding pocket that dictate entry and release of substrates. As compared with the conserved A141 of the S1 site and P188 of the S4 site in animal coronaviral Mpros, SARS-CoV-2 Mpro contains N142 and Q189 at equivalent positions which are considered to be more catalytically compatible. Furthermore, the conserved loop with residues 46-49 in animal coronaviral Mpros has been replaced by a stable α-helix in SARS-CoV-2 Mpro. In addition, the species-specific dimerization interface also influences the catalytic efficiency of CoV Mpros. Conclusively, the structural information of this study provides mechanistic insights into the ligand binding and dimerization of CoV Mpros among different species.

Molecular modelling and docking analysis of SARSCoV-2 helicase (yp-009725308) as drug target

Introduction: The ongoing outbreak of COVID-19 has become a global health emergency. The SARS-CoV-2 helicase (nsp13) play an important role in SARS-CoV-2 replication and could be serve as a target for antivirals to develop potential COVID-19 treatment. Objective: Homology modelling and docking analysis of SARSCoV-2 helicase (YP-009725308) as drug target. Methodology: The structure and function of SARSCoV-2 helicase (YP-009725308) predicted by in silico modelling studies. The SWISS-MODEL Structure Assessment tool was used for homology modelling and visual analysis of crystal structure of protein. The validation for structure models was performed by using PROCHECK. Model quality estimates based on the QMEAN and ProSA. The MCULE-1-Click docking, and InterEvDock-2.0 server were used for protein-ligand docking. Results: The SARS-CoV-2 helicase (YP-009725308) model corresponding to probability conformation with 90.9% residue of core section that specifies accuracy of predicted model. The ProSA Z-score score -9.17;indicates the good quality of the model. Inhibitor N-[3-(carbamoylamino) phenyl] acetamide exhibited effective binding affinity against helicase (YP-009725308). Docking studies revealed that Lys-146, Leu-147, Ile-151, Tyr-185, Lys-195, Tyr224, Val-226, Leu-227, Ser-229 are important residues for receptor-ligand interaction. Conclusion: Hence, the proposed inhibitor could potently inhibit SARS-CoV-2 helicase (YP-009725308) that recognized to play key roles during replication of viral RNAs. Overall findings demonstrate the SARS-CoV-2 helicase (nsp13) serve as a target for antivirals to cure COVID-19.

Application of bioinformatics, molecular dynamics simulations in biomedicines

Computation approach to drug discovery has Cbecome an important tool for understanding the mechanism of the interaction between the protein and inhibhitor complex. Different computational approach can be utilised for studying drug-delivery, stability of the protein and also in designing of vaccines. In the presentation, a brief discussion regarding the different tools used for studying the stability of a protein, drug delivery and designing vaccines will be discussed by giving examples from SARS-Cov2 as a model protein system. The effect of hydrophobic group, electron withdrawing effect, hydrogen bonding effect of the substituents present in the inhibitor effects the potency of the antagonist. Further, the stability of a protein, RNA can be analysed by studying the network analysis of the conformation evolution of the biomolecule. Immunoinformatic tools are also found to be important for designing vaccines as they help to identify B-cell, Tcell epitopes.